Ventilation Systems and Methods

ABSTRACT

This application describes methods and systems for ventilating a building. A method for ventilating a building includes drawing in air, using a central fan, for heating or cooling at least a portion of the building and exhausting air from the building using at least one exhaust fan. The exhaust fan can be automatically operated during time periods when the central fan is not switched on. The method further includes automatically opening a damper, during at least a portion of the time periods, such that fresh air enters the building through the damper

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.61/470,801, filed on Apr. 1, 2011, the entire content of which isincorporated herein by reference.

BACKGROUND

New energy efficient homes are being constructed almost air tight. Sotight they now need mechanical ventilation added to bring in just enoughfresh air to keep the occupants healthy.

ASHRAE (American Society of Heating and Refrigeration andAir-conditioning Engineers) provides a formula for the amount ofventilation: 7.5 cfm (N+1)+(A×0.01) where N=number of bedrooms, A=squarefootage of the home. So for example a 4 bedroom, 2,000 sq ft home wouldrequire: 7.5×5+(2,000×0.01)=57.5 CFM continuously of fresh air. Thehomes are measured for air leakage that can be subtracted from thecalculated requirement. For this example assume we measured 27.5 CFM ofleakage. That leaves 30 CFM we need to bring in continuously to meet theventilation standards. Coming standards are going to penalize buildersfor over ventilating so the more precise the method of control thebetter.

An inexpensive and effective method to bring in fresh air is to use thecentral fan and existing duct work from the heating and air-conditioningsystem to bleed in an amount of fresh air from an outside known sourceand distribute it throughout the home using a controller such as theAirCycler™ available from Lipidex Corporation of Marshfield, Mass.Techniques for accomplishing this are described in U.S. Pat. Nos.5,547,017 & 5,881,806 & 6,431,268, which are incorporated herein byreference.

With this known system you could bring in 90 cfm ⅓ of the time to meetthe 30 cfm continuous ventilation requirement. The AirCycler™ controlmonitors the thermostat and if it hasn't run ⅓ of the time from heatingor cooling, it will bring on the central fan to bring in the remainingrequirement of fresh air.

One issue with using the central fan to provide needed ventilation isthat a central fan will typically draw a lot of power (e.g. 400 W) tomove a relatively small amount of air. By contrast, a typical bathroomexhaust fan only uses 30 W.

U.S. Pat. No. 7,798,418, which is incorporated herein by reference,discloses three alternative methods for ventilating a space having acentral fan (for heating/cooling) and a bathroom exhaust fan.

Method 1:

the exhaust fan comes on whenever the central fan comes on. Thisprovides “balanced” ventilation. The central fan is used to bring airinto the building, and a bathroom exhaust ventilation fan is used toexhaust the same volume of air out of the building.

Some jurisdictions require “balanced” ventilation. They are concernedwith where the fresh air comes from when you exhaust stale air. In hothumid climates you don't want to depressurize a building because thatcould pull outside moisture into the walls.

In other jurisdictions, the balanced approach is not required, andventilation may be achieved by either only supplying fresh air (whichwill force out stale air by leakage out of the building), or by onlyexhausting stale air (which will be replaced by leakage into thebuilding).

Method 2:

the exhaust fan is turned on whenever the Central fan is off. The ideais you make up the required ventilation you're not getting when thecentral fan is off by turning on the ventilation fan. With thistechnique, you do not have to run the large expensive central fan forventilation, only heating and cooling. However this method could causeover-ventilation as a result of excess exhaust fan run time.

Method 3

the exhaust fan runs independently. A controller determines how manyminutes per hour to run the exhaust fan and it monitors fan run timewhen a person is in the bathroom manually operating the fan, includingthe “delay” time that the fan runs to continue after the person leaves,then subtracting that from the required time and making up thedifference.

One potential problem with home ventilation systems is the possibilitythat unhealthy air may be drawn into the building. For example, when anexhaust fan is operating, air may leak into the building from thegarage, and such air may include volatile organic hydrocarbons (VOCs),which are known to be carcinogenic.

Another potential problem with home ventilation systems is overventilation, whereby more fresh air than is desired or needed is broughtinto the building.

SUMMARY

In one aspect, the application describes a method for ventilating abuilding. The method includes drawing in air, using a central fan, forheating or cooling at least a portion of the building and exhausting airfrom the building using at least one exhaust fan. The exhaust fan can beautomatically operated during time periods when the central fan is notswitched on. The method further includes automatically opening a damper,during at least a portion of the time periods, such that fresh airenters the building through the damper.

In another aspect, the application describes a controller forcontrolling the ventilation of a building. In the building there are acentral fan configured to draw in air for heating or cooling at least aportion of the building, at least one exhaust fan adapted to exhaust airfrom the building, and a damper that, when opened, permits fresh air toenter the building. The controller includes control logic adapted togenerate signals to automatically operate the exhaust fan to exhaust airfrom the building during time periods when the central fan is notswitched on and to open the damper during at least a portion of the timeperiods, such that fresh air enters the building through the damper.

In another aspect, the application describes a method for ventilating abuilding. The method includes drawing in air, using a central fan, forheating or cooling at least a portion of the building. The central fanis automatically switched on during periods when a heating or coolingsystem is supplying hot or cold air to the building. The method alsoincludes expelling air from the building using at least one exhaust fansuch that the total amount of ventilation of the building resulting fromthe operation of the central fan and the exhaust fan is controlled toapproximate a predetermined amount. The exhaust fan is configured to beoperated during periods in which the central fan is not operational.

In another aspect, the application describes a controller forcontrolling the ventilation of a building having a central fan fordistributing air in a heating or cooling system and at least one exhaustfan. The controller includes a control logic adapted to generate signalsto operate the at least one exhaust fan during periods when the centralfan is not operational, so that the total amount of ventilation of thebuilding resulting from the operation of the central fan and the exhaustfan is controlled to approximate a predetermined amount.

Implementations can include one or more of the following.

Control signals can be received from the controller at the central fan,the at least one exhaust fan and the damper and these can be operated inaccordance with the control signals. The central fan can be switched onin accordance with one of the control signals when a heating or coolingsystem is operating to heat or cool a portion of the building. Theexhaust fan can be switched on in accordance with one of the controlsignals responsive to a manual input. The exhaust fan can be switchedoff after a predetermined time period. The damper can be automaticallyopened during a time period when the central fan is switched on. Theexhaust fan can be a bathroom exhaust fan. The exhaust fan can be akitchen exhaust fan.

The controller can be further adapted to generate signals to switch onthe central fan in accordance with an operation of a heating or coolingsystem. The controller can be adapted to generate signals to switch onthe exhaust fan responsive to a manual input. The controller can beadapted to generate signals to switch off the exhaust fan after apre-determined time period. The controller can be adapted to generatesignals to open the damper during a time period when the central fan isswitched on.

The at least one exhaust fan can be configured to be operated for afirst time period responsive to a manual input and automatically for asecond additional time period on determining that the exhaust fan is tobe operated for the second additional time period to achieve theapproximate predetermined amount of ventilation. Automatically operatingthe exhaust fan can include operating the exhaust fan during periodswhen the central fan is not switched on. A damper can be automaticallyopened to permit the inflow of fresh air into the building during thefirst time period or the second additional time period.

The exhaust fan can be part of a heat recovery ventilator (HRV) or anenergy recovery ventilator (ERV). The controller can be further adaptedto automatically open a damper during at least a portion of time periodswhen the exhaust fan is switched on, such that fresh air enters thebuilding through the damper.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a ventilation system.

FIG. 2 is a flowchart of an example process for operating a ventilationsystem.

FIG. 3 is a flowchart of an example process for operating a ventilationsystem.

FIG. 4 is a block diagram of a computing system.

DETAILED DESCRIPTION

The present application describes methods and systems for ventilating abuilding. Referring to FIG. 1, a ventilation system 100 of a buildingincludes a main or central fan 105 that is used for heating and/orcooling at least a portion of the building in connection with a heatingor air conditioning system, at least one exhaust fan 110 (such as abathroom or kitchen exhaust fan), and a damper 115 in communication withthe central fan, for example through a controller 120. The central fan105 can be disposed within the building or in a unit external to thebuilding. Fresh air is drawn in by the central fan 105 and circulated inthe building via one or more fresh air ducts 106. In someimplementations, air from within the building can be expelled orexhausted from the building through one or more exhaust ducts 108. Thecontroller 120 is usually disposed inside the building, for example on awall. The controller 120 may include an electronic controller such as amicrocontroller, microprocessor or a digital signal processor (DSP). Insome implementations, the exhaust fan 110 is switched on during timeperiods when the central fan 105 is not operating, in order to exhauststale air from the building. In some implementations, during at least aportion of those time periods, the damper 115 is automatically opened,so that fresh air enters the building through the damper, rather thanother, potentially less desirable, routes (e.g. via a leakage from thegarage). Even though the example of FIG. 1 illustrates that the damper115 is disposed in an intake duct 113 connected to the central fan 105,the damper 115 can also be disposed elsewhere in the building. Forexample, the damper can be disposed on an external wall of the buildingor in another duct or pipe that facilitates a flow of fresh air. Thecontroller 120 can be configured to send control signals to one or moreof the central fan 105, the exhaust fan 110, and the damper 115 tofacilitate the automatic operations (e.g. switching on or off). Forexample, the exhaust fan 110 may be automatically operated by thecontroller for certain time periods in addition to periods when theexhaust fan 110 is manually operated, for example, using a switch 113.In another example, the controller 120 may send one or more controlsignals to operate the central fan 105 when the heating or coolingsystem is operating. The controller 120 may also operate the exhaust fan110 when a person is using the bathroom (e.g., based on determining ifthe bathroom light is turned on), and potentially for a periodafterwards. The controller 120 may further operate the exhaust fan 110to perform any additional ventilation needed to achieve a desired amountof ventilation in the building over a predetermined time period (e.g. anhour, a day, or during normal work hours). In some implementations, theexhaust fan may be part of an energy recovery ventilator or a heatrecovery ventilator.

The controller 120 can also be configured to send control signals to thedamper 115 to automatically open or close the damper 115. In someimplementations, the controller 120 can be configured to open the damper115 during periods when the central fan 105 is operating. In someimplementations, the controller 120 can also be configured to open thedamper 115 during periods when the exhaust fan 110 is operating.

In some implementations, a user of the ventilation system 100 may enterthe desired continuous ventilation requirement, for example 30 CFM, intothe controller 120. The controller 120 may also be provided with ameasured exhaust fan ventilation flow rate and the central fan supplyflow rate in CFM. The controller 120 may then monitor the central fan105, tracking the amount of fresh air supplied to the home as a resultof heating and/or cooling operations. The controller 120 may also trackthe amount of fresh air supplied as a result of manual operation of theexhaust fan 110 (e.g., when a user is using the bathroom). If thedesired amount of ventilation in a given time period (e.g., one hour)was not reached from heating and cooling and the manual exhaust fanoperation, the controller 120 may calculate, based on for example, theprovided flow rates for the central and exhaust fans, an amount ofadditional ventilation still required to be made up by the exhaust fan110. The controller 120 then operates the exhaust fan 110 for anadditional period of time to achieve the additional amount ofventilation.

In one example, the central fan 105 brings in or circulates 120 CFM offresh air and the bathroom ventilation fan 110 exhausts or expels 90 CFMof air. If the desired ventilation rate is 30 CFM, the controller 120may calculate the additional ventilation needed as follows. In thisexample, the hourly requirements are 30 CFM×60 Minutes/hr=1,800 CubicFeet/hr. If the central fan runs for 10 minutes in a given hour, 120CFM×10 Min=1,200 CF of fresh air is brought in therefore leaving anadditional 600 CF to bring in. In this example, 600 CF/90 CFM=6.7minutes of additional ventilation operation of the exhaust fan 110 isneeded either at the end of the hour or within the hour to meet the1,800 CF/hr requirement.

During long heating and cooling runs, the controller 120 may close thedamper 115 to restrict the amount of fresh air to a predeterminedamount, thus preventing over ventilation. In some implementations,during periods of little or no heating or cooling, the controller 120provides the required ventilation by operating the exhaust fan 110,while also opening the motorized damper 115 in the fresh air duct to theair handler to provide pressure relief.

In a case where the central fan 105 comes on at the end of the hour (oranother predetermined period) while the exhaust fan 110 is running, thecontroller 120 may track the additional flow and subtract the additionalamount from the following hour or period, thus preventingover-ventilation. In another example, if the ventilation fan is operatedfor an excess amount of time (e.g., because of a long occupancy of thebathroom), the resulting excess ventilation amount may be subtractedfrom the desired ventilation in a following time period.

FIG. 2 is a flowchart 200 of an example process for operating aventilation system. In some implementations, the process represented bythe flowchart 200 can be implemented in the ventilation system 100described with reference to FIG. 1. Operations of the process caninclude circulating air, using a central fan, for heating or cooling atleast a portion of a building (202). Operations of the process alsoinclude exhausting air from the building using at least one exhaust fanthat is automatically operated during time periods when the central fanis not switched on (204). The automatic operation of the exhaust fan(s)with respect to the central fan can be controlled by a controller suchas the controller 120 described with reference to FIG. 1. Operations ofthe process further include automatically opening a damper during atleast a portion of the time periods (206). The damper is opened suchthat fresh air enters the building through the damper.

FIG. 3 is a flowchart 300 of an example process for operating aventilation system. In some implementations, the process represented bythe flowchart 300 can be implemented in the ventilation system 100described with reference to FIG. 1. Operations of the process includedrawing in air, using a central fan, for heating or cooling at least aportion of a building (302). The central fan can be switched on duringperiods when a heating or cooling system is supplying hot or cold air tothe building. Operations of the process also include expelling air fromthe building using at least one exhaust fan such that a predeterminedamount of ventilation is achieved (304).

FIG. 4 is a schematic diagram of a computer system 400 that can be usedto implement the controller described in association with any of thecomputer-implemented methods described herein, according to oneembodiment. The system 400 includes a processor 410, a memory 420, astorage device 430, and an input/output device 440. Each of thecomponents 410, 420, 430, and 440 are interconnected using a system bus450. The processor 410 is capable of processing instructions forexecution within the system 400. In one embodiment, the processor 410 isa single-threaded processor.

In another embodiment, the processor 410 is a multi-threaded processor.The processor 410 is capable of processing instructions stored in thememory 420 or on the storage device 430 to display graphical informationfor a user interface on the input/output device 440. In someimplementations, the processor 410 can be substantially similar to thecontroller 125 described above with reference to FIG. 10.

The memory 420 stores information within the system 400. In someembodiments, the memory 420 is a computer-readable storage medium. Thememory 420 can include volatile memory and/or non-volatile memory.

The storage device 430 is capable of providing mass storage for thesystem 400. In general, the storage device 430 can include anynon-transitory tangible media configured to store computer readableinstructions. In one embodiment, the storage device 430 is acomputer-readable medium. In various different embodiments, the storagedevice 430 may be a floppy disk device, a hard disk device, an opticaldisk device, or a tape device.

The input/output device 440 provides input/output operations for thesystem 400. In some embodiments, the input/output device 440 includes akeyboard and/or pointing device. In some embodiments, the input/outputdevice 440 includes a display unit for displaying graphical userinterfaces.

The features described in this application can be implemented in digitalelectronic circuitry, or in computer hardware, firmware, or incombinations of them. The features can be implemented in a computerprogram product tangibly embodied in an information carrier, e.g., in amachine-readable storage device, for execution by a programmableprocessor; and features can be performed by a programmable processorexecuting a program of instructions to perform functions of thedescribed embodiments by operating on input data and generating output.The described features can be implemented in one or more computerprograms that are executable on a programmable system including at leastone programmable processor coupled to receive data and instructionsfrom, and to transmit data and instructions to, a data storage system,at least one input device, and at least one output device. A computerprogram includes a set of instructions that can be used, directly orindirectly, in a computer to perform a certain activity or bring about acertain result. A computer program can be written in any form ofprogramming language, including compiled or interpreted languages, andit can be deployed in any form, including as a stand-alone program or asa module, component, subroutine, or other unit suitable for use in acomputing environment.

Generally, a computer will also include, or be operatively coupled tocommunicate with, one or more mass storage devices for storing datafiles; such devices include magnetic disks, such as internal hard disksand removable disks; magneto-optical disks; and optical disks. Storagedevices suitable for tangibly embodying computer program instructionsand data include all forms of non-volatile memory, including by way ofexample semiconductor memory devices, such as EPROM, EEPROM, and flashmemory devices; magnetic disks such as internal hard disks and removabledisks; magneto-optical disks; and CD-ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,ASICs (application-specific integrated circuits).

To provide for interaction with a user, the features can be implementedon a computer having a display device such as a CRT (cathode ray tube)or LCD (liquid crystal display) monitor for displaying information tothe user and a keyboard and a pointing device such as a mouse or atrackball by which the user can provide input to the computer.Alternatively, the computer can have no keyboard, mouse, or monitorattached and can be controlled remotely by another computer.

The features can be implemented in a computer system that includes aback-end component, such as a data server, or that includes a middlewarecomponent, such as an application server or an Internet server, or thatincludes a front-end component, such as a client computer having agraphical user interface or an Internet browser, or any combination ofthem. The components of the system can be connected by any form ormedium of digital data communication such as a communication network.Examples of communication networks include, e.g., a LAN, a WAN, and thecomputers and networks forming the Internet.

The computer system can include clients and servers. A client and serverare generally remote from each other and typically interact through anetwork. The relationship of client and server arises by virtue ofcomputer programs running on the respective computers and having aclient-server relationship to each other.

The processor 410 carries out instructions related to a computerprogram. The processor 410 can include hardware such as logic gates,adders, multipliers and counters. The processor 410 can further includea separate arithmetic logic unit (ALU) that performs arithmetic andlogical operations.

Other embodiments not explicitly described herein are also within thespirit of the invention and the scope of the claims. It will beunderstood by those skilled in the art that various changes in form anddetails may be made to the disclosed embodiments without departing fromthe spirit and scope of the invention as defined by the claims. Thoseskilled in the art will recognize or be able to ascertain using no morethan routine experimentation, many equivalents to the specificembodiments of the invention described specifically herein.

1. A method for ventilating a building, the method comprising: drawingin air, using a central fan, for heating or cooling at least a portionof the building; exhausting air from the building using at least oneexhaust fan, wherein the exhaust fan is automatically operated duringtime periods when the central fan is not switched on; and during atleast a portion of the time periods, automatically opening a damper,such that fresh air enters the building through the damper.
 2. Themethod of claim 1, further comprising: receiving control signals from acontroller at the central fan, the at least one exhaust fan and thedamper; and operating the central fan, the at least one exhaust fan, andthe damper in accordance with the control signals.
 3. The method ofclaim 2, further comprising switching on the central fan in accordancewith one of the control signals when a heating or cooling system isoperating to heat or cool the portion of the building.
 4. The method ofclaim 2, further comprising switching on the exhaust fan in accordancewith one of the control signals responsive to a manual input.
 5. Themethod of claim 4, further comprising switching off the exhaust fanafter a predetermined time period.
 6. The method of claim 1, furthercomprising automatically opening the damper during a time period whenthe central fan is switched on.
 7. The method of claim 1, wherein theexhaust fan is a bathroom exhaust fan.
 8. The method of claim 1, whereinthe exhaust fan is a kitchen exhaust fan.
 9. A controller forcontrolling the ventilation of a building in which there is a centralfan configured to draw in air for heating or cooling at least a portionof the building, at least one exhaust fan adapted to exhaust air fromthe building, and a damper that, when opened, permits fresh air to enterthe building, the controller comprising: a control logic adapted togenerate signals to automatically operate the exhaust fan to exhaust airfrom the building during time periods when the central fan is notswitched on and to open the damper during at least a portion of the timeperiods, such that fresh air enters the building through the damper. 10.The controller of claim 9, wherein the controller is further adapted togenerate signals to switch on the central fan in accordance with anoperation of a heating or cooling system.
 11. The controller of claim 9,wherein the controller is adapted to generate signals to switch on theexhaust fan responsive to a manual input.
 12. The controller of claim11, wherein the controller is adapted to generate signals to switch offthe exhaust fan after a pre-determined time period.
 13. The controllerof claim 9, wherein the controller is adapted to generate signals toopen the damper during a time period when the central fan is switchedon.
 14. The controller of claim 9, wherein the exhaust fan is a bathroomexhaust fan.
 15. The controller of claim 9, wherein the exhaust fan is akitchen exhaust fan.
 16. A method for ventilating a building, the methodcomprising: drawing in air, using a central fan, for heating or coolingat least a portion of the building, wherein the central fan isautomatically switched on during periods when a heating or coolingsystem is supplying hot or cold air to the building; and expelling airfrom the building using at least one exhaust fan, wherein the exhaustfan is configured to be operated during periods in which the central fanis not operational, such that the total amount of ventilation of thebuilding resulting from the operation of the central fan and the exhaustfan is controlled to approximate a predetermined amount.
 17. The methodof claim 16, wherein the at least one exhaust fan is configured to beoperated for a first time period responsive to a manual input andautomatically for a second additional time period on determining thatthe exhaust fan is to be operated for the second additional time periodto achieve the approximate predetermined amount of ventilation.
 18. Themethod of claim 17, wherein automatically operating the exhaust fancomprises operating the exhaust fan during periods when the central fanis not switched on.
 19. The method of claim 17, further comprisingautomatically opening a damper that permits the inflow of fresh air intothe building during the first time period or the second additional timeperiod.
 20. The method of claim 16, wherein the exhaust fan is part of aheat recovery ventilator (HRV) or an energy recovery ventilator (ERV).21. A controller for controlling the ventilation of a building having acentral fan for distributing air in a heating or cooling system and atleast one exhaust fan, the controller comprising: a control logicadapted to generate signals to operate the at least one exhaust fanduring periods when the central fan is not operational, so that thetotal amount of ventilation of the building resulting from the operationof the central fan and the exhaust fan is controlled to approximate apredetermined amount.
 22. The controller of claim 21, wherein thecontroller is further adapted to automatically open a damper during atleast a portion of time periods when the exhaust fan is switched on,such that fresh air enters the building through the damper.